The present work deals with the synthesis, characterization and cadmium adsorption studies on SiO 2 , Fe(OH) 3 and their mixed oxides. Mixed oxides of iron and silicon of composition [0.5M SiO 2 :0.5M Fe(OH) 3 ] were prepared by physical mixing (M 1 ) and sequential precipitation methods (M 2 ). The selectivity of adsorbents towards Cd 2+ ion was found to be in the order M 2 >M 1 =Fe(OH) 3 >silica. Dissolution of silica, mixed oxides M 1 and M 2 was also investigated in the pH range 3–10. The greater dissolution of mixed oxide M 2 , along with the higher selectivity towards Cd 2+ ions showed the formation of the ternary complexes on the surface of M 2 . The complex formation was also confirmed by IR studies and by the increase in Cd 2+ sorption with the addition of the silicates anions in the medium. The thermodynamic parameters showed the Cd 2+ sorption to be endothermic and spontaneous in nature.